Case No. IP-2019-000196

has the title “Method and apparatus for controlling a ventilator”, the ventilator being of the type used to assist a patient to breathe by delivering oxygen and removing carbon dioxide.2.The defendants (collectively “Hamilton”) make and sell ventilators. Some of the ventilators incorporate what is called the “Intellivent-ASV System”. Professor Tehrani alleges that the marketing of the Invellivent-ASV System has infringed the Patent.3.Hamilton deny infringement and counterclaim for revocation of the Patent on the grounds of lack of novelty, lack of inventive step and insufficiency.4.Mitchell Beebe appeared for Professor Tehrani, Henry Ward for Hamilton. The Witnesses 5.There were two expert witnesses. Prof. Tehrani gave expert evidence on her own behalf. Since 1994 Prof. Tehrani has been Professor of Electrical Engineering at California State University, Fullerton, California.6.There is no necessary reason why an expert should not be closely connected to the party for which he or she is giving evidence, such as being an employee. But in such instances there is an inevitable risk that the expert’s views could be coloured by loyalty to his or her employer. There may be a higher than usual requirement for the expert to show, by the answers given and manner in which they are given, that their clear and primary duty while giving evidence has been to assist the court objectively and truthfully. In this instance the expert was both claimant and inventor of the patent in suit. That requirement was more acute.7.I am sorry to say that Professor Tehrani did not provide the necessary indication of her objectivity. I think that she came to court to argue her case and that her evidence was given in that spirit. I do not suggest that Professor Tehrani had the intention of misleading the court, but it was my strong impression that she could persuade herself of the truth of matters that fitted her view of the case. It does not follow that she was wrong about such matters. However, I was not always sure that what she said was fair and accurate.8.I give an example. Professor Tehrani alleged that the work done by two teams who published papers, each of which was pleaded as an item of prior art, contained false research which had been forged. Three of the four members of one of those teams were physicians at Harvard Medical School. The other paper was written by an engineer from the Department of Electrical Engineering at the University of Wyoming and a physician at the Alaska Native Medical Center. Irrespective of the relevance of these allegations, they were serious, inherently unlikely to be true and were not shown to be true. Yet I do not doubt that Professor Tehrani believed her allegations to be accurate.9.I give a second example. In her first witness statement Professor Tehrani set out propositions which, she said, were part of the common general knowledge of the skilled person at the priority date. They were not supported by references to textbooks or anything else, they were just assertions. When challenged about this in cross-examination, her answer was to dismiss the idea that she had to support anything that was so obviously accepted by everyone in the field.10.All too often during cross-examination a challenge to something Professor Tehrani had said was likewise dismissed as a challenge borne solely of ignorance. Professor Tehrani did not give me confidence that her evidence was accurate and objective.11.Hamilton’s expert was Professor Stephen Rees. He is Professor at the Respiratory and Critical Care Group, Department of Health Science and Technology, Aalborg University in Denmark. Professor Rees’ carries out research in the development, validation and application of physiological models to solve problems arising in respiratory medicine. Counsel for Professor Tehrani rightly accepted that Professor Rees gave his answers fairly and was doing his best to help the court. I found Professor Rees to be an impressive and helpful witness. The technical background 12.The main function of the respiratory system is to regulate gases in the blood. Gas exchange occurs in the alveoli, very small air sacs in the lungs. Blood in the capillaries within the wall of the alveoli takes up oxygen in the inhaled air, while carbon dioxide is transferred from the capillaries to the air within the alveoli. That air is then exhaled. Meanwhile the oxygenated blood in the alveoli walls travels from the lungs to the heart where it is pumped to the organs of the body.13.Mechanical ventilation is required when a patient cannot breathe on their own, either satisfactorily or at all. This may be because they are undergoing surgery with anaesthesia or because of an illness. Some illnesses (such as covid-19, to use an example post-dating the priority date of the Patent) may lead to a life-threatening condition known as “acute respiratory distress syndrome” or “ARDS”, where the lungs cannot provide the body’s vital organs with enough oxygen. Ventilators are used to compensate.14.Ventilators consist of a mechanical pneumatic apparatus which delivers air to the patient, usually supplemented with oxygen. This mechanical function is controlled by an electronic system which also provides information to those monitoring the patient. The invention claimed in the Patent is concerned with an electronic system of that type.15.A ventilator has two functions. One is oxygenation: controlling the level of oxygen in the blood. The other is ventilation: eliminating carbon dioxide from the patient’s blood.16.The fraction of oxygen in the inspiratory gas delivered to the patient is called the “FiO2”. The lower the level of oxygen in the patient’s blood, the higher will be the FiO2, which may vary from 21%, i.e. the figure for air in its natural form, to 100% oxygen. The aim of oxygenating the patient’s blood is to increase the partial pressure of oxygen, “PaO2”, in the arterial blood. This is sometimes measured as the oxygen saturation or “SaO2”. Measuring either the PaO2 or the SaO2 of the patient may be invasive, so a proxy method can be used known as “pulse oximetry”. A pulse oximeter is a device with a probe which is clipped to a body part, usually a finger or ear lobe. The probe uses light to measure the level of oxygen in the blood, the “SpO2”. A typical SpO2 of a healthy person is in the region of 95-99%. The target SpO2 of a patient under ventilation is generally 88-95%.17.Another measure to be monitored is the level of carbon dioxide in the exhaled air. A “capnograph” is a device which measures the partial pressure of carbon dioxide at the end of an exhaled breath. Normal values are 5-6% CO2.18.The breathing of a patient using a ventilator may be “spontaneous”, meaning that the breaths are generated by the patient, albeit assisted by the ventilator. When the patient is unable to breathe spontaneously, the breaths are “mandatory”, fully controlled by the ventilator.19.A ventilator will deliver gas at a pressure higher than atmospheric pressure in order to inflate the patient’s lungs. This pressure is maintained, even at the end of the patient’s exhalation, to prevent collapse or partial collapse of the alveoli and is known as the “positive end-expiratory pressure”, or “PEEP”. Excessive PEEP is harmful so it is generally maintained within the range 5-25 cm H2O.20.The ventilator provides a prescribed volume of gas to the patient, known as the “tidal volume” or “VT”. The volume of air delivered to a patient per minute is the “minute volume”. It will vary and depends in part on the partial pressure of carbon dioxide in the patient’s blood. The rate at which gas is delivered by the ventilator is known as the “respiration frequency” or sometimes the “respiration rate”.21.When in mandatory mode, a ventilator is in control of the lengths of both inhalation and exhalation. The ratio of the two is known as the “I:E” and is typically 2. It is important to maintain an appropriate I:E to ensure that a tidal volume of gas delivered to the patient is removed before the next volume is delivered. Failure to maintain the correct I:E may lead to a build-up of trapped air in the lungs, generating pressure known as “auto-PEEP” or “intrinsic PEEP”.22.A significant balance which featured in the evidence was that between FiO2 and PEEP. Both affect the oxygen level of the patient’s blood and by the priority date it was well recognised that the balance is important to the maintenance of a satisfactory oxygen level.23.Professor Rees’ evidence was that at the priority date there were two well-known approaches to the manual adjustment of FiO2 and PEEP, i.e. adjustment by the clinician. One of these followed from what were known as the “ARDSnet studies”. These were published in the New England Journal of Medicine in 2000 in what Professor Rees called a seminal paper, which the skilled person would have read. He said that the paper generated considerable interest and discussion and had been incorporated into textbooks by the priority date. He exhibited a copy of the relevant section of one of the textbooks, Essentials of Mechanical Ventilation by Dean Hess and Robert Kacmarek, 2nd ed., pub. 2002.24.The ARDSnet studies provided a protocol for the treatment of patients with ARDS. Fixed value pairs for FiO2 and PEEP were devised. PEEP was then set according to the FiO2 required.25.Professor Rees also made the point that if either FiO2 or PEEP is adjusted, there will be a delay before any further adjustment is made because it will take time for the change to have an effect and to be monitored. He said that typically it takes about 30 seconds for a change in levels of oxygen in the mouth to be registered by a pulse oximeter on the patient’s finger and between 2 to 5 minutes for a completed change in oxygen level in the arterial blood. For that reason, manual changes in FiO2 (i.e. in a non-automated system) were not made more frequently than once every 30 seconds and generally less frequently. Changes in PEEP were made incrementally to avoid excessive PEEP, with a delay of at least 20 minutes between changes, more often one to two hours.26.At the priority date of the Patent, some ventilators used a “closed-loop system”. The concept pre-dates its use in ventilators. The operator of a closed-loop system sets a target value for a variable. The target is achieved and then maintained using feedback from a sensor. A component within the system, a controller, compares a measured value of the variable with the target value, producing an error value. The error value determines an output value, the application of which causes adjustment to the variable towards the target value.27.By the priority date closed-loop control of PEEP and FiO2 in ventilators had been developed. One known means of automatic control was by use of a proportional, integral and derivative (“PID”) controller. The details of PID controllers do not matter; it is enough to say that they helped to avoid an overshoot of the target. The Skilled Person 28.Professor Tehrani characterised the skilled person as an electrical or mechanical engineer with an interest in automatic control systems for mechanical ventilators.29.Professor Rees suggested that one must consider a skilled team, the engineer being accompanied by a respiratory or critical care physician.30.It probably makes little difference since an engineer working in this field would regularly consult such a physician to ensure that they knew how mechanical ventilators could and would fit the requirements of the physician. To ensure that the physician’s knowledge is not forgotten, I think it is better to consider the matters in issue in this claim through the eyes of a skilled team as suggested by Professor Rees. The Common General Knowledge 31.It was not in dispute that the matters I have set out in the technical background would have formed part of the skilled person’s common general knowledge (“CGK”), subject to the following qualifications.32.Professor Tehrani said that the ARDSnet studies and the Hess and Kacmarek textbook would not have been part of the skilled engineer’s CGK. But she did not deny that they would have formed part of the CGK of the respiratory or critical care physician, whom I have found to be part of the skilled team.33.Professor Rees’ evidence was that all closed-loop systems used for ventilators were trial-and-error systems, in that measurements detected whether there was an “error’, a discrepancy between the patient’s condition and a target, and provided signals to move the patient towards the target. 34.Professor Tehrani relied on a paper she had written in 2008 to draw a distinction between trial-and-error systems and continuous systems as understood at the priority date. She amplified this in section 5 of her second report:“h) Trial-and-error, and continuous closed-loop automatic control systems (including PID systems) have [e]stablished definitions in the art, are fundamentally different, function on the basis of very different principles, and cannot be combined. Claiming that they can be combined as done in [Professor Rees’ first report], is against scientific principles, is erroneous, and misleads the court.”35.Although this was not easy to follow, my understanding of the distinction drawn by Professor Tehrani in her section 5 was that trial-and-error systems are all intermittent, in that appropriate PEEP and FiO2 are determined at intervals. She distinguished these from continuous systems in which the determination is more frequent. In closing, Professor Tehrani’s counsel put it a different way, presumably on instructions. The distinction was between a protocol-driven system, in which PEEP and FiO2 are driven by a protocol. In a trial-and-error system there is a target.36.To my mind, Professor Tehrani’s counsel was generating a distinction without a difference. The system is set up to have various conditions of the patient fall within desired values. If a discrepancy is detected between the patient’s conditions and those values, the system alters PEEP and FiO2 to drive the conditions towards compliance with those values. What might be described as a protocol may be involved, but that makes no difference to the principle of how the system works.37.There may be a distinction between systems which alter PEEP and FiO2 at greater or lesser intervals, although there must be a continuous spectrum of possible intervals. Assuming such a distinction would have been drawn by the skilled person at the priority date, which was not made clear, it does not undermine Professor Rees’ evidence that all were regarded as trial-and-error systems. I accept that evidence.38.Professor Rees said that it was part of the CGK that PEEP and FiO2 could be determined and changed each at different frequencies and indeed it was likely that PEEP would be altered less frequently. Professor Tehrani said that they would not be changed at different frequencies. Professor Tehrani’s view appeared to be based solely on her expressed opinion regarding the likely behaviour of clinicians. Professor Rees’ evidence was based on a sound reason for a difference in frequency, namely the safety of the patient for the reasons referred to above, and I accept his evidence. The Patent 39.The Patent has an unchallenged priority date of 21 November 2003. Claims 1, 29, 40 and 45 were said to be independently valid and each of them infringed. On the evidence presented, claims 29 and 40 stood or fell with claim 1. Accordingly, argument centred on claims 1 and 45 and I will discuss just those two claims.40.Paragraph [0002] explains that ventilators of the prior art require clinicians to make important selections among the options made available by advanced ventilators. Paragraphs [0003] and [0004] discuss published prior art in which attempts were made to automatically control some of the main outputs of ventilators. Continuing in paragraph [0005] the Patent says:“[0005] Some of the prior art on this subject is focused on controlling the patient’s oxygenation, and some is intended to automatically control the breathing frequency and tidal volume. The systems intended for controlling only the oxygen level of the patient on the ventilator, either do not provide the automation of all factors that affect oxygenation and/or they do not provide a reliable and sufficiently robust response against oxygen disturbance.”41.Paragraph [0007] explains the basic form of the invention. The term “continuous positive airway pressure” or “CPAP” is sometimes used in the Patent as an alternative for PEEP:“[0007] In one embodiment, the present invention describes a method and apparatus that can reliably and robustly control PEEP (or CPAP) and FiO2. These are novel features which significantly improve the oxygenation of patients during ventilatory therapy provided by mechanical ventilators as well as respiratory devices such as CPAP machines.”42.This first embodiment is about the control of oxygenation. A more elaborate embodiment is described in paragraph [0008] which, as that paragraph states, incorporates features of US Patent No. 4,986,268 (“US 268”) into the first embodiment. US 268 was, before it expired, a patent owned by Professor Tehrani and concerns a control scheme for ventilation.43.A block diagram of an embodiment of the more elaborate scheme disclosed in the Patent is shown in Figure 1: 44.The oxygen sensor (30) is preferably a pulse oximeter. It receives information from the patient (40) and produces output (24).45.The carbon-dioxide sensor (32), preferably a capnograph, produces another output (26).46.A lung mechanics calculator and pressure volume (“PV”) monitor (34) produces three outputs, collectively shown as (28). They are (i) respiratory elastance, (ii) respiratory airway resistance and (iii) the lower inflection point on the inspiratory or expiratory PV curve of the patient, or alternatively the patient’s intrinsic PEEP.47.Each of the signals (24), (26) and (28) passes to the digital processor (10) via a converter (analogue to digital, (18), (20) and (22)). The digital processor controls a signal generator circuit (46) which provides at least two signals. The first (48) is a signal to control PEEP, breathing frequency, tidal volume and I:E ratio, which is transmitted to the mechanical ventilator (56). The ventilator responds accordingly. The second signal from the signal generator (50) passes to the ventilator via a mixer regulator (58) and an oxygen air mixer (62). It controls the FiO2 of the gas which the ventilator sends to the patient. In extreme cases the inputs (12), (14) and (16) will lead the signal generator circuit to send an alarm signal (52). Claim 1 48.This is claim 1 divided into integers:“1A An apparatus for automatically controlling a ventilator comprising:1B first means for processing data indicative of at least a measured oxygen level of a patient, and for providing output data indicative of:1C required concentration of oxygen in inspiratory gas of the patient (FiO2) and positive end-expiratory pressure (PEEP) for a next breath of the patient;1D wherein FiO2 is determined to reduce the difference between the measured oxygen level of the patient and a desired value;1E wherein PEEP is determined to keep a ratio of PEEP/FiO2 within a prescribed range and, while keeping the ratio within the prescribed range, to keep the measured oxygen level of the patient above a predefined value; and1F second means, operatively coupled to the first means, for providing control signals, based on the output data provided by the first means, to the ventilator;1G wherein the control signals provided to the ventilator automatically control PEEP, and FiO2, for a next breath of the patient.”49.In broad summary, claim 45 adds to claim 1 the requirement that the apparatus controlling the ventilator controls not only the PEEP and FiO2, i.e. oxygenation, but also ventilation including breathing frequency and I:E ratio:“45A An apparatus for automatically controlling a ventilator comprising:45B (a) means for providing data indicative of the measured oxygen level of the patient;45C (b) means for providing data indicative of the measured carbon dioxide level of the patient;45D (c) means for providing data indicative of respiratory elastance, and respiratory airway resistance of the patient;45E (d) a programmable controller storing executable instructions that when executed perform the steps of:45F (I) determining, from the data indicative of the measured oxygen level of the patient provided by (a), a required concentration of oxygen in an inspiratory gas of the patient, FiO2, to reduce a difference between the measured oxygen level of the patient and a desired value, and providing a data signal indicative of the required FiO2;45G (II) determining a required positive end-expiratory pressure, PEEP, and providing a data signal indicative of the required PEEP, wherein the required PEEP maintains a ratio of PEEP/ FiO2 within a prescribed range, and while the ratio is maintained within the prescribed range, to keep the measured oxygen level of the patient above a predefined value;45H (III) determining, based upon the data provided by (a), (b), and (c), an optimal breathing frequency, a required ventilation, and a required adjustment in inspiration to expiration time ratio, I:E, for a next breath of the patient, and providing data signals indicative of the same; and,45I (e) means for providing to the ventilator, based upon the data signals provided by (I), (II) and (III), final data signals for automatically controlling: (i) the required FiO2, the required PEEP, (iii) the optimal breathing frequency, (iv) the required ventilation, (v) the required adjustment in I:E ratio, for a next breath of the patient.”